GenEx: Add expressions to specify build- or install-only values

This is for specifying INCLUDE_DIRECTORIES relevant to the build-location
or the install location for example:

 set_property(TARGET foo PROPERTY
   INTERFACE_INCLUDE_DIRECTORIES
   "$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR};${CMAKE_CURRENT_SOURCE_DIR}>"
   "$<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/include>"
 )

A 'bar' target can then use:

 set_property(TARGET bar PROPERTY
   INCLUDE_DIRECTORIES
   "$<TARGET_PROPERTY:foo,INTERFACE_INCLUDE_DIRECTORIES>"
 )

and it will work whether foo is in the same project, or an imported target
from an installation location, or an imported target from a build location
generated by the export() command.

Because the generator expressions are only evaluated at build-time, these
new expressions are equivalent to the ZeroNode and OneNode.

The GeneratorExpression test is split into parts. Some shells can't run
the custom command as it is getting too long.

4 files changed, 99 insertions, 9 deletions

diff --git a/Source/cmDocumentGeneratorExpressions.h b/Source/cmDocumentGeneratorExpressions.h
index 445fd0e..1927012 100644
--- a/Source/cmDocumentGeneratorExpressions.h
+++ b/Source/cmDocumentGeneratorExpressions.h
@@ -26,6 +26,12 @@
   "strings which contain a '>' for example.\n"                          \
   "  $<COMMA>                  = A literal ','. Used to compare "       \
   "strings which contain a ',' for example.\n"                          \
+  "  $<INSTALL_INTERFACE:...>  = content of \"...\" when the property " \
+  "is exported using install(EXPORT), and empty otherwise.\n"           \
+  "  $<BUILD_INTERFACE:...>    = content of \"...\" when the property " \
+  "is exported using export(), or when the target is used by another "  \
+  "target in the same buildsystem. Expands to the empty string "        \
+  "otherwise.\n"                                                        \
   "  $<TARGET_FILE:tgt>        = main file (.exe, .so.1.2, .a)\n"       \
   "  $<TARGET_LINKER_FILE:tgt> = file used to link (.a, .lib, .so)\n"   \
   "  $<TARGET_SONAME_FILE:tgt> = file with soname (.so.3)\n"            \
diff --git a/Source/cmGeneratorExpression.cxx b/Source/cmGeneratorExpression.cxx
index 3fd4a5f..841fbb7 100644
--- a/Source/cmGeneratorExpression.cxx
+++ b/Source/cmGeneratorExpression.cxx
@@ -123,15 +123,9 @@ cmCompiledGeneratorExpression::~cmCompiledGeneratorExpression()
     }
 }
 
-std::string cmGeneratorExpression::Preprocess(const std::string &input,
-                                              PreprocessContext context)
+//----------------------------------------------------------------------------
+static std::string stripAllGeneratorExpressions(const std::string &input)
 {
-  if (context != StripAllGeneratorExpressions)
-  {
-    assert(!"cmGeneratorExpression::Preprocess called with invalid args");
-    return std::string();
-  }
-
   std::string result;
   std::string::size_type pos = 0;
   std::string::size_type lastPos = pos;
@@ -170,3 +164,81 @@ std::string cmGeneratorExpression::Preprocess(const std::string &input,
   result += input.substr(lastPos);
   return result;
 }
+
+//----------------------------------------------------------------------------
+static std::string stripExportInterface(const std::string &input,
+                          cmGeneratorExpression::PreprocessContext context)
+{
+  std::string result;
+
+  std::string::size_type pos = 0;
+  std::string::size_type lastPos = pos;
+  while((pos = input.find("$<BUILD_INTERFACE:", lastPos)) != input.npos
+    || (pos = input.find("$<INSTALL_INTERFACE:", lastPos)) != input.npos)
+    {
+    result += input.substr(lastPos, pos - lastPos);
+    const bool gotInstallInterface = input[pos + 2] == 'I';
+    pos += gotInstallInterface ? sizeof("$<INSTALL_INTERFACE:") - 1
+                               : sizeof("$<BUILD_INTERFACE:") - 1;
+    int nestingLevel = 1;
+    const char *c = input.c_str() + pos;
+    const char * const cStart = c;
+    for ( ; *c; ++c)
+      {
+      if(c[0] == '$' && c[1] == '<')
+        {
+        ++nestingLevel;
+        ++c;
+        continue;
+        }
+      if(c[0] == '>')
+        {
+        --nestingLevel;
+        if (nestingLevel != 0)
+          {
+          continue;
+          }
+        if(context == cmGeneratorExpression::BuildInterface
+            && !gotInstallInterface)
+          {
+          result += input.substr(pos, c - cStart);
+          }
+        else if(context == cmGeneratorExpression::InstallInterface
+            && gotInstallInterface)
+          {
+          result += input.substr(pos, c - cStart);
+          }
+        break;
+        }
+      }
+    const std::string::size_type traversed = (c - cStart) + 1;
+    if (!*c)
+      {
+      result += std::string(gotInstallInterface ? "$<INSTALL_INTERFACE:"
+                                                : "$<BUILD_INTERFACE:")
+             + input.substr(pos, traversed);
+      }
+    pos += traversed;
+    lastPos = pos;
+    }
+  result += input.substr(lastPos);
+
+  return result;
+}
+
+//----------------------------------------------------------------------------
+std::string cmGeneratorExpression::Preprocess(const std::string &input,
+                                              PreprocessContext context)
+{
+  if (context == StripAllGeneratorExpressions)
+    {
+    return stripAllGeneratorExpressions(input);
+    }
+  else if (context == BuildInterface || context == InstallInterface)
+    {
+    return stripExportInterface(input, context);
+    }
+
+  assert(!"cmGeneratorExpression::Preprocess called with invalid args");
+  return std::string();
+}
diff --git a/Source/cmGeneratorExpression.h b/Source/cmGeneratorExpression.h
index 15e637c..99056a5 100644
--- a/Source/cmGeneratorExpression.h
+++ b/Source/cmGeneratorExpression.h
@@ -51,7 +51,9 @@ public:
   cmsys::auto_ptr<cmCompiledGeneratorExpression> Parse(const char* input);
 
   enum PreprocessContext {
-    StripAllGeneratorExpressions
+    StripAllGeneratorExpressions,
+    BuildInterface,
+    InstallInterface
   };
 
   static std::string Preprocess(const std::string &input,
diff --git a/Source/cmGeneratorExpressionEvaluator.cxx b/Source/cmGeneratorExpressionEvaluator.cxx
index 3b7cfc0..e20e203 100644
--- a/Source/cmGeneratorExpressionEvaluator.cxx
+++ b/Source/cmGeneratorExpressionEvaluator.cxx
@@ -96,6 +96,12 @@ static const struct OneNode : public cmGeneratorExpressionNode
 } oneNode;
 
 //----------------------------------------------------------------------------
+static const struct OneNode buildInterfaceNode;
+
+//----------------------------------------------------------------------------
+static const struct ZeroNode installInterfaceNode;
+
+//----------------------------------------------------------------------------
 #define BOOLEAN_OP_NODE(OPNAME, OP, SUCCESS_VALUE, FAILURE_VALUE) \
 static const struct OP ## Node : public cmGeneratorExpressionNode \
 { \
@@ -593,6 +599,10 @@ cmGeneratorExpressionNode* GetNode(const std::string &identifier)
     return &commaNode;
   else if (identifier == "TARGET_PROPERTY")
     return &targetPropertyNode;
+  else if (identifier == "BUILD_INTERFACE")
+    return &buildInterfaceNode;
+  else if (identifier == "INSTALL_INTERFACE")
+    return &installInterfaceNode;
   return 0;
 
 }